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Diffstat (limited to 'contrib/llvm/lib/Transforms/Scalar/LICM.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/Scalar/LICM.cpp | 2317 |
1 files changed, 0 insertions, 2317 deletions
diff --git a/contrib/llvm/lib/Transforms/Scalar/LICM.cpp b/contrib/llvm/lib/Transforms/Scalar/LICM.cpp deleted file mode 100644 index d9dda4cef2d2..000000000000 --- a/contrib/llvm/lib/Transforms/Scalar/LICM.cpp +++ /dev/null @@ -1,2317 +0,0 @@ -//===-- LICM.cpp - Loop Invariant Code Motion Pass ------------------------===// -// -// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. -// See https://llvm.org/LICENSE.txt for license information. -// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception -// -//===----------------------------------------------------------------------===// -// -// This pass performs loop invariant code motion, attempting to remove as much -// code from the body of a loop as possible. It does this by either hoisting -// code into the preheader block, or by sinking code to the exit blocks if it is -// safe. This pass also promotes must-aliased memory locations in the loop to -// live in registers, thus hoisting and sinking "invariant" loads and stores. -// -// This pass uses alias analysis for two purposes: -// -// 1. Moving loop invariant loads and calls out of loops. If we can determine -// that a load or call inside of a loop never aliases anything stored to, -// we can hoist it or sink it like any other instruction. -// 2. Scalar Promotion of Memory - If there is a store instruction inside of -// the loop, we try to move the store to happen AFTER the loop instead of -// inside of the loop. This can only happen if a few conditions are true: -// A. The pointer stored through is loop invariant -// B. There are no stores or loads in the loop which _may_ alias the -// pointer. There are no calls in the loop which mod/ref the pointer. -// If these conditions are true, we can promote the loads and stores in the -// loop of the pointer to use a temporary alloca'd variable. We then use -// the SSAUpdater to construct the appropriate SSA form for the value. -// -//===----------------------------------------------------------------------===// - -#include "llvm/Transforms/Scalar/LICM.h" -#include "llvm/ADT/SetOperations.h" -#include "llvm/ADT/Statistic.h" -#include "llvm/Analysis/AliasAnalysis.h" -#include "llvm/Analysis/AliasSetTracker.h" -#include "llvm/Analysis/BasicAliasAnalysis.h" -#include "llvm/Analysis/CaptureTracking.h" -#include "llvm/Analysis/ConstantFolding.h" -#include "llvm/Analysis/GlobalsModRef.h" -#include "llvm/Analysis/GuardUtils.h" -#include "llvm/Analysis/Loads.h" -#include "llvm/Analysis/LoopInfo.h" -#include "llvm/Analysis/LoopIterator.h" -#include "llvm/Analysis/LoopPass.h" -#include "llvm/Analysis/MemoryBuiltins.h" -#include "llvm/Analysis/MemorySSA.h" -#include "llvm/Analysis/MemorySSAUpdater.h" -#include "llvm/Analysis/OptimizationRemarkEmitter.h" -#include "llvm/Analysis/ScalarEvolution.h" -#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h" -#include "llvm/Analysis/TargetLibraryInfo.h" -#include "llvm/Analysis/ValueTracking.h" -#include "llvm/IR/CFG.h" -#include "llvm/IR/Constants.h" -#include "llvm/IR/DataLayout.h" -#include "llvm/IR/DebugInfoMetadata.h" -#include "llvm/IR/DerivedTypes.h" -#include "llvm/IR/Dominators.h" -#include "llvm/IR/Instructions.h" -#include "llvm/IR/IntrinsicInst.h" -#include "llvm/IR/LLVMContext.h" -#include "llvm/IR/Metadata.h" -#include "llvm/IR/PatternMatch.h" -#include "llvm/IR/PredIteratorCache.h" -#include "llvm/Support/CommandLine.h" -#include "llvm/Support/Debug.h" -#include "llvm/Support/raw_ostream.h" -#include "llvm/Transforms/Scalar.h" -#include "llvm/Transforms/Scalar/LoopPassManager.h" -#include "llvm/Transforms/Utils/BasicBlockUtils.h" -#include "llvm/Transforms/Utils/Local.h" -#include "llvm/Transforms/Utils/LoopUtils.h" -#include "llvm/Transforms/Utils/SSAUpdater.h" -#include <algorithm> -#include <utility> -using namespace llvm; - -#define DEBUG_TYPE "licm" - -STATISTIC(NumCreatedBlocks, "Number of blocks created"); -STATISTIC(NumClonedBranches, "Number of branches cloned"); -STATISTIC(NumSunk, "Number of instructions sunk out of loop"); -STATISTIC(NumHoisted, "Number of instructions hoisted out of loop"); -STATISTIC(NumMovedLoads, "Number of load insts hoisted or sunk"); -STATISTIC(NumMovedCalls, "Number of call insts hoisted or sunk"); -STATISTIC(NumPromoted, "Number of memory locations promoted to registers"); - -/// Memory promotion is enabled by default. -static cl::opt<bool> - DisablePromotion("disable-licm-promotion", cl::Hidden, cl::init(false), - cl::desc("Disable memory promotion in LICM pass")); - -static cl::opt<bool> ControlFlowHoisting( - "licm-control-flow-hoisting", cl::Hidden, cl::init(false), - cl::desc("Enable control flow (and PHI) hoisting in LICM")); - -static cl::opt<uint32_t> MaxNumUsesTraversed( - "licm-max-num-uses-traversed", cl::Hidden, cl::init(8), - cl::desc("Max num uses visited for identifying load " - "invariance in loop using invariant start (default = 8)")); - -// Default value of zero implies we use the regular alias set tracker mechanism -// instead of the cross product using AA to identify aliasing of the memory -// location we are interested in. -static cl::opt<int> -LICMN2Theshold("licm-n2-threshold", cl::Hidden, cl::init(0), - cl::desc("How many instruction to cross product using AA")); - -// Experimental option to allow imprecision in LICM in pathological cases, in -// exchange for faster compile. This is to be removed if MemorySSA starts to -// address the same issue. This flag applies only when LICM uses MemorySSA -// instead on AliasSetTracker. LICM calls MemorySSAWalker's -// getClobberingMemoryAccess, up to the value of the Cap, getting perfect -// accuracy. Afterwards, LICM will call into MemorySSA's getDefiningAccess, -// which may not be precise, since optimizeUses is capped. The result is -// correct, but we may not get as "far up" as possible to get which access is -// clobbering the one queried. -cl::opt<unsigned> llvm::SetLicmMssaOptCap( - "licm-mssa-optimization-cap", cl::init(100), cl::Hidden, - cl::desc("Enable imprecision in LICM in pathological cases, in exchange " - "for faster compile. Caps the MemorySSA clobbering calls.")); - -// Experimentally, memory promotion carries less importance than sinking and -// hoisting. Limit when we do promotion when using MemorySSA, in order to save -// compile time. -cl::opt<unsigned> llvm::SetLicmMssaNoAccForPromotionCap( - "licm-mssa-max-acc-promotion", cl::init(250), cl::Hidden, - cl::desc("[LICM & MemorySSA] When MSSA in LICM is disabled, this has no " - "effect. When MSSA in LICM is enabled, then this is the maximum " - "number of accesses allowed to be present in a loop in order to " - "enable memory promotion.")); - -static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI); -static bool isNotUsedOrFreeInLoop(const Instruction &I, const Loop *CurLoop, - const LoopSafetyInfo *SafetyInfo, - TargetTransformInfo *TTI, bool &FreeInLoop); -static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop, - BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo, - MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE); -static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT, - const Loop *CurLoop, ICFLoopSafetyInfo *SafetyInfo, - MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE); -static bool isSafeToExecuteUnconditionally(Instruction &Inst, - const DominatorTree *DT, - const Loop *CurLoop, - const LoopSafetyInfo *SafetyInfo, - OptimizationRemarkEmitter *ORE, - const Instruction *CtxI = nullptr); -static bool pointerInvalidatedByLoop(MemoryLocation MemLoc, - AliasSetTracker *CurAST, Loop *CurLoop, - AliasAnalysis *AA); -static bool pointerInvalidatedByLoopWithMSSA(MemorySSA *MSSA, MemoryUse *MU, - Loop *CurLoop, - SinkAndHoistLICMFlags &Flags); -static Instruction *CloneInstructionInExitBlock( - Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI, - const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU); - -static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo, - AliasSetTracker *AST, MemorySSAUpdater *MSSAU); - -static void moveInstructionBefore(Instruction &I, Instruction &Dest, - ICFLoopSafetyInfo &SafetyInfo, - MemorySSAUpdater *MSSAU); - -namespace { -struct LoopInvariantCodeMotion { - using ASTrackerMapTy = DenseMap<Loop *, std::unique_ptr<AliasSetTracker>>; - bool runOnLoop(Loop *L, AliasAnalysis *AA, LoopInfo *LI, DominatorTree *DT, - TargetLibraryInfo *TLI, TargetTransformInfo *TTI, - ScalarEvolution *SE, MemorySSA *MSSA, - OptimizationRemarkEmitter *ORE, bool DeleteAST); - - ASTrackerMapTy &getLoopToAliasSetMap() { return LoopToAliasSetMap; } - LoopInvariantCodeMotion(unsigned LicmMssaOptCap, - unsigned LicmMssaNoAccForPromotionCap) - : LicmMssaOptCap(LicmMssaOptCap), - LicmMssaNoAccForPromotionCap(LicmMssaNoAccForPromotionCap) {} - -private: - ASTrackerMapTy LoopToAliasSetMap; - unsigned LicmMssaOptCap; - unsigned LicmMssaNoAccForPromotionCap; - - std::unique_ptr<AliasSetTracker> - collectAliasInfoForLoop(Loop *L, LoopInfo *LI, AliasAnalysis *AA); - std::unique_ptr<AliasSetTracker> - collectAliasInfoForLoopWithMSSA(Loop *L, AliasAnalysis *AA, - MemorySSAUpdater *MSSAU); -}; - -struct LegacyLICMPass : public LoopPass { - static char ID; // Pass identification, replacement for typeid - LegacyLICMPass( - unsigned LicmMssaOptCap = SetLicmMssaOptCap, - unsigned LicmMssaNoAccForPromotionCap = SetLicmMssaNoAccForPromotionCap) - : LoopPass(ID), LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap) { - initializeLegacyLICMPassPass(*PassRegistry::getPassRegistry()); - } - - bool runOnLoop(Loop *L, LPPassManager &LPM) override { - if (skipLoop(L)) { - // If we have run LICM on a previous loop but now we are skipping - // (because we've hit the opt-bisect limit), we need to clear the - // loop alias information. - LICM.getLoopToAliasSetMap().clear(); - return false; - } - - auto *SE = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>(); - MemorySSA *MSSA = EnableMSSALoopDependency - ? (&getAnalysis<MemorySSAWrapperPass>().getMSSA()) - : nullptr; - // For the old PM, we can't use OptimizationRemarkEmitter as an analysis - // pass. Function analyses need to be preserved across loop transformations - // but ORE cannot be preserved (see comment before the pass definition). - OptimizationRemarkEmitter ORE(L->getHeader()->getParent()); - return LICM.runOnLoop(L, - &getAnalysis<AAResultsWrapperPass>().getAAResults(), - &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(), - &getAnalysis<DominatorTreeWrapperPass>().getDomTree(), - &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(), - &getAnalysis<TargetTransformInfoWrapperPass>().getTTI( - *L->getHeader()->getParent()), - SE ? &SE->getSE() : nullptr, MSSA, &ORE, false); - } - - /// This transformation requires natural loop information & requires that - /// loop preheaders be inserted into the CFG... - /// - void getAnalysisUsage(AnalysisUsage &AU) const override { - AU.addPreserved<DominatorTreeWrapperPass>(); - AU.addPreserved<LoopInfoWrapperPass>(); - AU.addRequired<TargetLibraryInfoWrapperPass>(); - if (EnableMSSALoopDependency) { - AU.addRequired<MemorySSAWrapperPass>(); - AU.addPreserved<MemorySSAWrapperPass>(); - } - AU.addRequired<TargetTransformInfoWrapperPass>(); - getLoopAnalysisUsage(AU); - } - - using llvm::Pass::doFinalization; - - bool doFinalization() override { - auto &AliasSetMap = LICM.getLoopToAliasSetMap(); - // All loops in the AliasSetMap should be cleaned up already. The only case - // where we fail to do so is if an outer loop gets deleted before LICM - // visits it. - assert(all_of(AliasSetMap, - [](LoopInvariantCodeMotion::ASTrackerMapTy::value_type &KV) { - return !KV.first->getParentLoop(); - }) && - "Didn't free loop alias sets"); - AliasSetMap.clear(); - return false; - } - -private: - LoopInvariantCodeMotion LICM; - - /// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info. - void cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, - Loop *L) override; - - /// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias - /// set. - void deleteAnalysisValue(Value *V, Loop *L) override; - - /// Simple Analysis hook. Delete loop L from alias set map. - void deleteAnalysisLoop(Loop *L) override; -}; -} // namespace - -PreservedAnalyses LICMPass::run(Loop &L, LoopAnalysisManager &AM, - LoopStandardAnalysisResults &AR, LPMUpdater &) { - const auto &FAM = - AM.getResult<FunctionAnalysisManagerLoopProxy>(L, AR).getManager(); - Function *F = L.getHeader()->getParent(); - - auto *ORE = FAM.getCachedResult<OptimizationRemarkEmitterAnalysis>(*F); - // FIXME: This should probably be optional rather than required. - if (!ORE) - report_fatal_error("LICM: OptimizationRemarkEmitterAnalysis not " - "cached at a higher level"); - - LoopInvariantCodeMotion LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap); - if (!LICM.runOnLoop(&L, &AR.AA, &AR.LI, &AR.DT, &AR.TLI, &AR.TTI, &AR.SE, - AR.MSSA, ORE, true)) - return PreservedAnalyses::all(); - - auto PA = getLoopPassPreservedAnalyses(); - - PA.preserve<DominatorTreeAnalysis>(); - PA.preserve<LoopAnalysis>(); - if (EnableMSSALoopDependency) - PA.preserve<MemorySSAAnalysis>(); - - return PA; -} - -char LegacyLICMPass::ID = 0; -INITIALIZE_PASS_BEGIN(LegacyLICMPass, "licm", "Loop Invariant Code Motion", - false, false) -INITIALIZE_PASS_DEPENDENCY(LoopPass) -INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) -INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) -INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass) -INITIALIZE_PASS_END(LegacyLICMPass, "licm", "Loop Invariant Code Motion", false, - false) - -Pass *llvm::createLICMPass() { return new LegacyLICMPass(); } -Pass *llvm::createLICMPass(unsigned LicmMssaOptCap, - unsigned LicmMssaNoAccForPromotionCap) { - return new LegacyLICMPass(LicmMssaOptCap, LicmMssaNoAccForPromotionCap); -} - -/// Hoist expressions out of the specified loop. Note, alias info for inner -/// loop is not preserved so it is not a good idea to run LICM multiple -/// times on one loop. -/// We should delete AST for inner loops in the new pass manager to avoid -/// memory leak. -/// -bool LoopInvariantCodeMotion::runOnLoop( - Loop *L, AliasAnalysis *AA, LoopInfo *LI, DominatorTree *DT, - TargetLibraryInfo *TLI, TargetTransformInfo *TTI, ScalarEvolution *SE, - MemorySSA *MSSA, OptimizationRemarkEmitter *ORE, bool DeleteAST) { - bool Changed = false; - - assert(L->isLCSSAForm(*DT) && "Loop is not in LCSSA form."); - - std::unique_ptr<AliasSetTracker> CurAST; - std::unique_ptr<MemorySSAUpdater> MSSAU; - bool NoOfMemAccTooLarge = false; - unsigned LicmMssaOptCounter = 0; - - if (!MSSA) { - LLVM_DEBUG(dbgs() << "LICM: Using Alias Set Tracker.\n"); - CurAST = collectAliasInfoForLoop(L, LI, AA); - } else { - LLVM_DEBUG(dbgs() << "LICM: Using MemorySSA.\n"); - MSSAU = make_unique<MemorySSAUpdater>(MSSA); - - unsigned AccessCapCount = 0; - for (auto *BB : L->getBlocks()) { - if (auto *Accesses = MSSA->getBlockAccesses(BB)) { - for (const auto &MA : *Accesses) { - (void)MA; - AccessCapCount++; - if (AccessCapCount > LicmMssaNoAccForPromotionCap) { - NoOfMemAccTooLarge = true; - break; - } - } - } - if (NoOfMemAccTooLarge) - break; - } - } - - // Get the preheader block to move instructions into... - BasicBlock *Preheader = L->getLoopPreheader(); - - // Compute loop safety information. - ICFLoopSafetyInfo SafetyInfo(DT); - SafetyInfo.computeLoopSafetyInfo(L); - - // We want to visit all of the instructions in this loop... that are not parts - // of our subloops (they have already had their invariants hoisted out of - // their loop, into this loop, so there is no need to process the BODIES of - // the subloops). - // - // Traverse the body of the loop in depth first order on the dominator tree so - // that we are guaranteed to see definitions before we see uses. This allows - // us to sink instructions in one pass, without iteration. After sinking - // instructions, we perform another pass to hoist them out of the loop. - SinkAndHoistLICMFlags Flags = {NoOfMemAccTooLarge, LicmMssaOptCounter, - LicmMssaOptCap, LicmMssaNoAccForPromotionCap, - /*IsSink=*/true}; - if (L->hasDedicatedExits()) - Changed |= sinkRegion(DT->getNode(L->getHeader()), AA, LI, DT, TLI, TTI, L, - CurAST.get(), MSSAU.get(), &SafetyInfo, Flags, ORE); - Flags.IsSink = false; - if (Preheader) - Changed |= hoistRegion(DT->getNode(L->getHeader()), AA, LI, DT, TLI, L, - CurAST.get(), MSSAU.get(), &SafetyInfo, Flags, ORE); - - // Now that all loop invariants have been removed from the loop, promote any - // memory references to scalars that we can. - // Don't sink stores from loops without dedicated block exits. Exits - // containing indirect branches are not transformed by loop simplify, - // make sure we catch that. An additional load may be generated in the - // preheader for SSA updater, so also avoid sinking when no preheader - // is available. - if (!DisablePromotion && Preheader && L->hasDedicatedExits() && - !NoOfMemAccTooLarge) { - // Figure out the loop exits and their insertion points - SmallVector<BasicBlock *, 8> ExitBlocks; - L->getUniqueExitBlocks(ExitBlocks); - - // We can't insert into a catchswitch. - bool HasCatchSwitch = llvm::any_of(ExitBlocks, [](BasicBlock *Exit) { - return isa<CatchSwitchInst>(Exit->getTerminator()); - }); - - if (!HasCatchSwitch) { - SmallVector<Instruction *, 8> InsertPts; - SmallVector<MemoryAccess *, 8> MSSAInsertPts; - InsertPts.reserve(ExitBlocks.size()); - if (MSSAU) - MSSAInsertPts.reserve(ExitBlocks.size()); - for (BasicBlock *ExitBlock : ExitBlocks) { - InsertPts.push_back(&*ExitBlock->getFirstInsertionPt()); - if (MSSAU) - MSSAInsertPts.push_back(nullptr); - } - - PredIteratorCache PIC; - - bool Promoted = false; - - // Build an AST using MSSA. - if (!CurAST.get()) - CurAST = collectAliasInfoForLoopWithMSSA(L, AA, MSSAU.get()); - - // Loop over all of the alias sets in the tracker object. - for (AliasSet &AS : *CurAST) { - // We can promote this alias set if it has a store, if it is a "Must" - // alias set, if the pointer is loop invariant, and if we are not - // eliminating any volatile loads or stores. - if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() || - !L->isLoopInvariant(AS.begin()->getValue())) - continue; - - assert( - !AS.empty() && - "Must alias set should have at least one pointer element in it!"); - - SmallSetVector<Value *, 8> PointerMustAliases; - for (const auto &ASI : AS) - PointerMustAliases.insert(ASI.getValue()); - - Promoted |= promoteLoopAccessesToScalars( - PointerMustAliases, ExitBlocks, InsertPts, MSSAInsertPts, PIC, LI, - DT, TLI, L, CurAST.get(), MSSAU.get(), &SafetyInfo, ORE); - } - - // Once we have promoted values across the loop body we have to - // recursively reform LCSSA as any nested loop may now have values defined - // within the loop used in the outer loop. - // FIXME: This is really heavy handed. It would be a bit better to use an - // SSAUpdater strategy during promotion that was LCSSA aware and reformed - // it as it went. - if (Promoted) - formLCSSARecursively(*L, *DT, LI, SE); - - Changed |= Promoted; - } - } - - // Check that neither this loop nor its parent have had LCSSA broken. LICM is - // specifically moving instructions across the loop boundary and so it is - // especially in need of sanity checking here. - assert(L->isLCSSAForm(*DT) && "Loop not left in LCSSA form after LICM!"); - assert((!L->getParentLoop() || L->getParentLoop()->isLCSSAForm(*DT)) && - "Parent loop not left in LCSSA form after LICM!"); - - // If this loop is nested inside of another one, save the alias information - // for when we process the outer loop. - if (!MSSAU.get() && CurAST.get() && L->getParentLoop() && !DeleteAST) - LoopToAliasSetMap[L] = std::move(CurAST); - - if (MSSAU.get() && VerifyMemorySSA) - MSSAU->getMemorySSA()->verifyMemorySSA(); - - if (Changed && SE) - SE->forgetLoopDispositions(L); - return Changed; -} - -/// Walk the specified region of the CFG (defined by all blocks dominated by -/// the specified block, and that are in the current loop) in reverse depth -/// first order w.r.t the DominatorTree. This allows us to visit uses before -/// definitions, allowing us to sink a loop body in one pass without iteration. -/// -bool llvm::sinkRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI, - DominatorTree *DT, TargetLibraryInfo *TLI, - TargetTransformInfo *TTI, Loop *CurLoop, - AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU, - ICFLoopSafetyInfo *SafetyInfo, - SinkAndHoistLICMFlags &Flags, - OptimizationRemarkEmitter *ORE) { - - // Verify inputs. - assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && - CurLoop != nullptr && SafetyInfo != nullptr && - "Unexpected input to sinkRegion."); - assert(((CurAST != nullptr) ^ (MSSAU != nullptr)) && - "Either AliasSetTracker or MemorySSA should be initialized."); - - // We want to visit children before parents. We will enque all the parents - // before their children in the worklist and process the worklist in reverse - // order. - SmallVector<DomTreeNode *, 16> Worklist = collectChildrenInLoop(N, CurLoop); - - bool Changed = false; - for (DomTreeNode *DTN : reverse(Worklist)) { - BasicBlock *BB = DTN->getBlock(); - // Only need to process the contents of this block if it is not part of a - // subloop (which would already have been processed). - if (inSubLoop(BB, CurLoop, LI)) - continue; - - for (BasicBlock::iterator II = BB->end(); II != BB->begin();) { - Instruction &I = *--II; - - // If the instruction is dead, we would try to sink it because it isn't - // used in the loop, instead, just delete it. - if (isInstructionTriviallyDead(&I, TLI)) { - LLVM_DEBUG(dbgs() << "LICM deleting dead inst: " << I << '\n'); - salvageDebugInfo(I); - ++II; - eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); - Changed = true; - continue; - } - - // Check to see if we can sink this instruction to the exit blocks - // of the loop. We can do this if the all users of the instruction are - // outside of the loop. In this case, it doesn't even matter if the - // operands of the instruction are loop invariant. - // - bool FreeInLoop = false; - if (isNotUsedOrFreeInLoop(I, CurLoop, SafetyInfo, TTI, FreeInLoop) && - canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, MSSAU, true, &Flags, - ORE) && - !I.mayHaveSideEffects()) { - if (sink(I, LI, DT, CurLoop, SafetyInfo, MSSAU, ORE)) { - if (!FreeInLoop) { - ++II; - eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); - } - Changed = true; - } - } - } - } - if (MSSAU && VerifyMemorySSA) - MSSAU->getMemorySSA()->verifyMemorySSA(); - return Changed; -} - -namespace { -// This is a helper class for hoistRegion to make it able to hoist control flow -// in order to be able to hoist phis. The way this works is that we initially -// start hoisting to the loop preheader, and when we see a loop invariant branch -// we make note of this. When we then come to hoist an instruction that's -// conditional on such a branch we duplicate the branch and the relevant control -// flow, then hoist the instruction into the block corresponding to its original -// block in the duplicated control flow. -class ControlFlowHoister { -private: - // Information about the loop we are hoisting from - LoopInfo *LI; - DominatorTree *DT; - Loop *CurLoop; - MemorySSAUpdater *MSSAU; - - // A map of blocks in the loop to the block their instructions will be hoisted - // to. - DenseMap<BasicBlock *, BasicBlock *> HoistDestinationMap; - - // The branches that we can hoist, mapped to the block that marks a - // convergence point of their control flow. - DenseMap<BranchInst *, BasicBlock *> HoistableBranches; - -public: - ControlFlowHoister(LoopInfo *LI, DominatorTree *DT, Loop *CurLoop, - MemorySSAUpdater *MSSAU) - : LI(LI), DT(DT), CurLoop(CurLoop), MSSAU(MSSAU) {} - - void registerPossiblyHoistableBranch(BranchInst *BI) { - // We can only hoist conditional branches with loop invariant operands. - if (!ControlFlowHoisting || !BI->isConditional() || - !CurLoop->hasLoopInvariantOperands(BI)) - return; - - // The branch destinations need to be in the loop, and we don't gain - // anything by duplicating conditional branches with duplicate successors, - // as it's essentially the same as an unconditional branch. - BasicBlock *TrueDest = BI->getSuccessor(0); - BasicBlock *FalseDest = BI->getSuccessor(1); - if (!CurLoop->contains(TrueDest) || !CurLoop->contains(FalseDest) || - TrueDest == FalseDest) - return; - - // We can hoist BI if one branch destination is the successor of the other, - // or both have common successor which we check by seeing if the - // intersection of their successors is non-empty. - // TODO: This could be expanded to allowing branches where both ends - // eventually converge to a single block. - SmallPtrSet<BasicBlock *, 4> TrueDestSucc, FalseDestSucc; - TrueDestSucc.insert(succ_begin(TrueDest), succ_end(TrueDest)); - FalseDestSucc.insert(succ_begin(FalseDest), succ_end(FalseDest)); - BasicBlock *CommonSucc = nullptr; - if (TrueDestSucc.count(FalseDest)) { - CommonSucc = FalseDest; - } else if (FalseDestSucc.count(TrueDest)) { - CommonSucc = TrueDest; - } else { - set_intersect(TrueDestSucc, FalseDestSucc); - // If there's one common successor use that. - if (TrueDestSucc.size() == 1) - CommonSucc = *TrueDestSucc.begin(); - // If there's more than one pick whichever appears first in the block list - // (we can't use the value returned by TrueDestSucc.begin() as it's - // unpredicatable which element gets returned). - else if (!TrueDestSucc.empty()) { - Function *F = TrueDest->getParent(); - auto IsSucc = [&](BasicBlock &BB) { return TrueDestSucc.count(&BB); }; - auto It = std::find_if(F->begin(), F->end(), IsSucc); - assert(It != F->end() && "Could not find successor in function"); - CommonSucc = &*It; - } - } - // The common successor has to be dominated by the branch, as otherwise - // there will be some other path to the successor that will not be - // controlled by this branch so any phi we hoist would be controlled by the - // wrong condition. This also takes care of avoiding hoisting of loop back - // edges. - // TODO: In some cases this could be relaxed if the successor is dominated - // by another block that's been hoisted and we can guarantee that the - // control flow has been replicated exactly. - if (CommonSucc && DT->dominates(BI, CommonSucc)) - HoistableBranches[BI] = CommonSucc; - } - - bool canHoistPHI(PHINode *PN) { - // The phi must have loop invariant operands. - if (!ControlFlowHoisting || !CurLoop->hasLoopInvariantOperands(PN)) - return false; - // We can hoist phis if the block they are in is the target of hoistable - // branches which cover all of the predecessors of the block. - SmallPtrSet<BasicBlock *, 8> PredecessorBlocks; - BasicBlock *BB = PN->getParent(); - for (BasicBlock *PredBB : predecessors(BB)) - PredecessorBlocks.insert(PredBB); - // If we have less predecessor blocks than predecessors then the phi will - // have more than one incoming value for the same block which we can't - // handle. - // TODO: This could be handled be erasing some of the duplicate incoming - // values. - if (PredecessorBlocks.size() != pred_size(BB)) - return false; - for (auto &Pair : HoistableBranches) { - if (Pair.second == BB) { - // Which blocks are predecessors via this branch depends on if the - // branch is triangle-like or diamond-like. - if (Pair.first->getSuccessor(0) == BB) { - PredecessorBlocks.erase(Pair.first->getParent()); - PredecessorBlocks.erase(Pair.first->getSuccessor(1)); - } else if (Pair.first->getSuccessor(1) == BB) { - PredecessorBlocks.erase(Pair.first->getParent()); - PredecessorBlocks.erase(Pair.first->getSuccessor(0)); - } else { - PredecessorBlocks.erase(Pair.first->getSuccessor(0)); - PredecessorBlocks.erase(Pair.first->getSuccessor(1)); - } - } - } - // PredecessorBlocks will now be empty if for every predecessor of BB we - // found a hoistable branch source. - return PredecessorBlocks.empty(); - } - - BasicBlock *getOrCreateHoistedBlock(BasicBlock *BB) { - if (!ControlFlowHoisting) - return CurLoop->getLoopPreheader(); - // If BB has already been hoisted, return that - if (HoistDestinationMap.count(BB)) - return HoistDestinationMap[BB]; - - // Check if this block is conditional based on a pending branch - auto HasBBAsSuccessor = - [&](DenseMap<BranchInst *, BasicBlock *>::value_type &Pair) { - return BB != Pair.second && (Pair.first->getSuccessor(0) == BB || - Pair.first->getSuccessor(1) == BB); - }; - auto It = std::find_if(HoistableBranches.begin(), HoistableBranches.end(), - HasBBAsSuccessor); - - // If not involved in a pending branch, hoist to preheader - BasicBlock *InitialPreheader = CurLoop->getLoopPreheader(); - if (It == HoistableBranches.end()) { - LLVM_DEBUG(dbgs() << "LICM using " << InitialPreheader->getName() - << " as hoist destination for " << BB->getName() - << "\n"); - HoistDestinationMap[BB] = InitialPreheader; - return InitialPreheader; - } - BranchInst *BI = It->first; - assert(std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) == - HoistableBranches.end() && - "BB is expected to be the target of at most one branch"); - - LLVMContext &C = BB->getContext(); - BasicBlock *TrueDest = BI->getSuccessor(0); - BasicBlock *FalseDest = BI->getSuccessor(1); - BasicBlock *CommonSucc = HoistableBranches[BI]; - BasicBlock *HoistTarget = getOrCreateHoistedBlock(BI->getParent()); - - // Create hoisted versions of blocks that currently don't have them - auto CreateHoistedBlock = [&](BasicBlock *Orig) { - if (HoistDestinationMap.count(Orig)) - return HoistDestinationMap[Orig]; - BasicBlock *New = - BasicBlock::Create(C, Orig->getName() + ".licm", Orig->getParent()); - HoistDestinationMap[Orig] = New; - DT->addNewBlock(New, HoistTarget); - if (CurLoop->getParentLoop()) - CurLoop->getParentLoop()->addBasicBlockToLoop(New, *LI); - ++NumCreatedBlocks; - LLVM_DEBUG(dbgs() << "LICM created " << New->getName() - << " as hoist destination for " << Orig->getName() - << "\n"); - return New; - }; - BasicBlock *HoistTrueDest = CreateHoistedBlock(TrueDest); - BasicBlock *HoistFalseDest = CreateHoistedBlock(FalseDest); - BasicBlock *HoistCommonSucc = CreateHoistedBlock(CommonSucc); - - // Link up these blocks with branches. - if (!HoistCommonSucc->getTerminator()) { - // The new common successor we've generated will branch to whatever that - // hoist target branched to. - BasicBlock *TargetSucc = HoistTarget->getSingleSuccessor(); - assert(TargetSucc && "Expected hoist target to have a single successor"); - HoistCommonSucc->moveBefore(TargetSucc); - BranchInst::Create(TargetSucc, HoistCommonSucc); - } - if (!HoistTrueDest->getTerminator()) { - HoistTrueDest->moveBefore(HoistCommonSucc); - BranchInst::Create(HoistCommonSucc, HoistTrueDest); - } - if (!HoistFalseDest->getTerminator()) { - HoistFalseDest->moveBefore(HoistCommonSucc); - BranchInst::Create(HoistCommonSucc, HoistFalseDest); - } - - // If BI is being cloned to what was originally the preheader then - // HoistCommonSucc will now be the new preheader. - if (HoistTarget == InitialPreheader) { - // Phis in the loop header now need to use the new preheader. - InitialPreheader->replaceSuccessorsPhiUsesWith(HoistCommonSucc); - if (MSSAU) - MSSAU->wireOldPredecessorsToNewImmediatePredecessor( - HoistTarget->getSingleSuccessor(), HoistCommonSucc, {HoistTarget}); - // The new preheader dominates the loop header. - DomTreeNode *PreheaderNode = DT->getNode(HoistCommonSucc); - DomTreeNode *HeaderNode = DT->getNode(CurLoop->getHeader()); - DT->changeImmediateDominator(HeaderNode, PreheaderNode); - // The preheader hoist destination is now the new preheader, with the - // exception of the hoist destination of this branch. - for (auto &Pair : HoistDestinationMap) - if (Pair.second == InitialPreheader && Pair.first != BI->getParent()) - Pair.second = HoistCommonSucc; - } - - // Now finally clone BI. - ReplaceInstWithInst( - HoistTarget->getTerminator(), - BranchInst::Create(HoistTrueDest, HoistFalseDest, BI->getCondition())); - ++NumClonedBranches; - - assert(CurLoop->getLoopPreheader() && - "Hoisting blocks should not have destroyed preheader"); - return HoistDestinationMap[BB]; - } -}; -} // namespace - -/// Walk the specified region of the CFG (defined by all blocks dominated by -/// the specified block, and that are in the current loop) in depth first -/// order w.r.t the DominatorTree. This allows us to visit definitions before -/// uses, allowing us to hoist a loop body in one pass without iteration. -/// -bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI, - DominatorTree *DT, TargetLibraryInfo *TLI, Loop *CurLoop, - AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU, - ICFLoopSafetyInfo *SafetyInfo, - SinkAndHoistLICMFlags &Flags, - OptimizationRemarkEmitter *ORE) { - // Verify inputs. - assert(N != nullptr && AA != nullptr && LI != nullptr && DT != nullptr && - CurLoop != nullptr && SafetyInfo != nullptr && - "Unexpected input to hoistRegion."); - assert(((CurAST != nullptr) ^ (MSSAU != nullptr)) && - "Either AliasSetTracker or MemorySSA should be initialized."); - - ControlFlowHoister CFH(LI, DT, CurLoop, MSSAU); - - // Keep track of instructions that have been hoisted, as they may need to be - // re-hoisted if they end up not dominating all of their uses. - SmallVector<Instruction *, 16> HoistedInstructions; - - // For PHI hoisting to work we need to hoist blocks before their successors. - // We can do this by iterating through the blocks in the loop in reverse - // post-order. - LoopBlocksRPO Worklist(CurLoop); - Worklist.perform(LI); - bool Changed = false; - for (BasicBlock *BB : Worklist) { - // Only need to process the contents of this block if it is not part of a - // subloop (which would already have been processed). - if (inSubLoop(BB, CurLoop, LI)) - continue; - - for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) { - Instruction &I = *II++; - // Try constant folding this instruction. If all the operands are - // constants, it is technically hoistable, but it would be better to - // just fold it. - if (Constant *C = ConstantFoldInstruction( - &I, I.getModule()->getDataLayout(), TLI)) { - LLVM_DEBUG(dbgs() << "LICM folding inst: " << I << " --> " << *C - << '\n'); - if (CurAST) - CurAST->copyValue(&I, C); - // FIXME MSSA: Such replacements may make accesses unoptimized (D51960). - I.replaceAllUsesWith(C); - if (isInstructionTriviallyDead(&I, TLI)) - eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); - Changed = true; - continue; - } - - // Try hoisting the instruction out to the preheader. We can only do - // this if all of the operands of the instruction are loop invariant and - // if it is safe to hoist the instruction. - // TODO: It may be safe to hoist if we are hoisting to a conditional block - // and we have accurately duplicated the control flow from the loop header - // to that block. - if (CurLoop->hasLoopInvariantOperands(&I) && - canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, MSSAU, true, &Flags, - ORE) && - isSafeToExecuteUnconditionally( - I, DT, CurLoop, SafetyInfo, ORE, - CurLoop->getLoopPreheader()->getTerminator())) { - hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo, - MSSAU, ORE); - HoistedInstructions.push_back(&I); - Changed = true; - continue; - } - - // Attempt to remove floating point division out of the loop by - // converting it to a reciprocal multiplication. - if (I.getOpcode() == Instruction::FDiv && - CurLoop->isLoopInvariant(I.getOperand(1)) && - I.hasAllowReciprocal()) { - auto Divisor = I.getOperand(1); - auto One = llvm::ConstantFP::get(Divisor->getType(), 1.0); - auto ReciprocalDivisor = BinaryOperator::CreateFDiv(One, Divisor); - ReciprocalDivisor->setFastMathFlags(I.getFastMathFlags()); - SafetyInfo->insertInstructionTo(ReciprocalDivisor, I.getParent()); - ReciprocalDivisor->insertBefore(&I); - - auto Product = - BinaryOperator::CreateFMul(I.getOperand(0), ReciprocalDivisor); - Product->setFastMathFlags(I.getFastMathFlags()); - SafetyInfo->insertInstructionTo(Product, I.getParent()); - Product->insertAfter(&I); - I.replaceAllUsesWith(Product); - eraseInstruction(I, *SafetyInfo, CurAST, MSSAU); - - hoist(*ReciprocalDivisor, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), - SafetyInfo, MSSAU, ORE); - HoistedInstructions.push_back(ReciprocalDivisor); - Changed = true; - continue; - } - - auto IsInvariantStart = [&](Instruction &I) { - using namespace PatternMatch; - return I.use_empty() && - match(&I, m_Intrinsic<Intrinsic::invariant_start>()); - }; - auto MustExecuteWithoutWritesBefore = [&](Instruction &I) { - return SafetyInfo->isGuaranteedToExecute(I, DT, CurLoop) && - SafetyInfo->doesNotWriteMemoryBefore(I, CurLoop); - }; - if ((IsInvariantStart(I) || isGuard(&I)) && - CurLoop->hasLoopInvariantOperands(&I) && - MustExecuteWithoutWritesBefore(I)) { - hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo, - MSSAU, ORE); - HoistedInstructions.push_back(&I); - Changed = true; - continue; - } - - if (PHINode *PN = dyn_cast<PHINode>(&I)) { - if (CFH.canHoistPHI(PN)) { - // Redirect incoming blocks first to ensure that we create hoisted - // versions of those blocks before we hoist the phi. - for (unsigned int i = 0; i < PN->getNumIncomingValues(); ++i) - PN->setIncomingBlock( - i, CFH.getOrCreateHoistedBlock(PN->getIncomingBlock(i))); - hoist(*PN, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo, - MSSAU, ORE); - assert(DT->dominates(PN, BB) && "Conditional PHIs not expected"); - Changed = true; - continue; - } - } - - // Remember possibly hoistable branches so we can actually hoist them - // later if needed. - if (BranchInst *BI = dyn_cast<BranchInst>(&I)) - CFH.registerPossiblyHoistableBranch(BI); - } - } - - // If we hoisted instructions to a conditional block they may not dominate - // their uses that weren't hoisted (such as phis where some operands are not - // loop invariant). If so make them unconditional by moving them to their - // immediate dominator. We iterate through the instructions in reverse order - // which ensures that when we rehoist an instruction we rehoist its operands, - // and also keep track of where in the block we are rehoisting to to make sure - // that we rehoist instructions before the instructions that use them. - Instruction *HoistPoint = nullptr; - if (ControlFlowHoisting) { - for (Instruction *I : reverse(HoistedInstructions)) { - if (!llvm::all_of(I->uses(), - [&](Use &U) { return DT->dominates(I, U); })) { - BasicBlock *Dominator = - DT->getNode(I->getParent())->getIDom()->getBlock(); - if (!HoistPoint || !DT->dominates(HoistPoint->getParent(), Dominator)) { - if (HoistPoint) - assert(DT->dominates(Dominator, HoistPoint->getParent()) && - "New hoist point expected to dominate old hoist point"); - HoistPoint = Dominator->getTerminator(); - } - LLVM_DEBUG(dbgs() << "LICM rehoisting to " - << HoistPoint->getParent()->getName() - << ": " << *I << "\n"); - moveInstructionBefore(*I, *HoistPoint, *SafetyInfo, MSSAU); - HoistPoint = I; - Changed = true; - } - } - } - if (MSSAU && VerifyMemorySSA) - MSSAU->getMemorySSA()->verifyMemorySSA(); - - // Now that we've finished hoisting make sure that LI and DT are still - // valid. -#ifndef NDEBUG - if (Changed) { - assert(DT->verify(DominatorTree::VerificationLevel::Fast) && - "Dominator tree verification failed"); - LI->verify(*DT); - } -#endif - - return Changed; -} - -// Return true if LI is invariant within scope of the loop. LI is invariant if -// CurLoop is dominated by an invariant.start representing the same memory -// location and size as the memory location LI loads from, and also the -// invariant.start has no uses. -static bool isLoadInvariantInLoop(LoadInst *LI, DominatorTree *DT, - Loop *CurLoop) { - Value *Addr = LI->getOperand(0); - const DataLayout &DL = LI->getModule()->getDataLayout(); - const uint32_t LocSizeInBits = DL.getTypeSizeInBits(LI->getType()); - - // if the type is i8 addrspace(x)*, we know this is the type of - // llvm.invariant.start operand - auto *PtrInt8Ty = PointerType::get(Type::getInt8Ty(LI->getContext()), - LI->getPointerAddressSpace()); - unsigned BitcastsVisited = 0; - // Look through bitcasts until we reach the i8* type (this is invariant.start - // operand type). - while (Addr->getType() != PtrInt8Ty) { - auto *BC = dyn_cast<BitCastInst>(Addr); - // Avoid traversing high number of bitcast uses. - if (++BitcastsVisited > MaxNumUsesTraversed || !BC) - return false; - Addr = BC->getOperand(0); - } - - unsigned UsesVisited = 0; - // Traverse all uses of the load operand value, to see if invariant.start is - // one of the uses, and whether it dominates the load instruction. - for (auto *U : Addr->users()) { - // Avoid traversing for Load operand with high number of users. - if (++UsesVisited > MaxNumUsesTraversed) - return false; - IntrinsicInst *II = dyn_cast<IntrinsicInst>(U); - // If there are escaping uses of invariant.start instruction, the load maybe - // non-invariant. - if (!II || II->getIntrinsicID() != Intrinsic::invariant_start || - !II->use_empty()) - continue; - unsigned InvariantSizeInBits = - cast<ConstantInt>(II->getArgOperand(0))->getSExtValue() * 8; - // Confirm the invariant.start location size contains the load operand size - // in bits. Also, the invariant.start should dominate the load, and we - // should not hoist the load out of a loop that contains this dominating - // invariant.start. - if (LocSizeInBits <= InvariantSizeInBits && - DT->properlyDominates(II->getParent(), CurLoop->getHeader())) - return true; - } - - return false; -} - -namespace { -/// Return true if-and-only-if we know how to (mechanically) both hoist and -/// sink a given instruction out of a loop. Does not address legality -/// concerns such as aliasing or speculation safety. -bool isHoistableAndSinkableInst(Instruction &I) { - // Only these instructions are hoistable/sinkable. - return (isa<LoadInst>(I) || isa<StoreInst>(I) || isa<CallInst>(I) || - isa<FenceInst>(I) || isa<BinaryOperator>(I) || isa<CastInst>(I) || - isa<SelectInst>(I) || isa<GetElementPtrInst>(I) || isa<CmpInst>(I) || - isa<InsertElementInst>(I) || isa<ExtractElementInst>(I) || - isa<ShuffleVectorInst>(I) || isa<ExtractValueInst>(I) || - isa<InsertValueInst>(I)); -} -/// Return true if all of the alias sets within this AST are known not to -/// contain a Mod, or if MSSA knows thare are no MemoryDefs in the loop. -bool isReadOnly(AliasSetTracker *CurAST, const MemorySSAUpdater *MSSAU, - const Loop *L) { - if (CurAST) { - for (AliasSet &AS : *CurAST) { - if (!AS.isForwardingAliasSet() && AS.isMod()) { - return false; - } - } - return true; - } else { /*MSSAU*/ - for (auto *BB : L->getBlocks()) - if (MSSAU->getMemorySSA()->getBlockDefs(BB)) - return false; - return true; - } -} - -/// Return true if I is the only Instruction with a MemoryAccess in L. -bool isOnlyMemoryAccess(const Instruction *I, const Loop *L, - const MemorySSAUpdater *MSSAU) { - for (auto *BB : L->getBlocks()) - if (auto *Accs = MSSAU->getMemorySSA()->getBlockAccesses(BB)) { - int NotAPhi = 0; - for (const auto &Acc : *Accs) { - if (isa<MemoryPhi>(&Acc)) - continue; - const auto *MUD = cast<MemoryUseOrDef>(&Acc); - if (MUD->getMemoryInst() != I || NotAPhi++ == 1) - return false; - } - } - return true; -} -} - -bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT, - Loop *CurLoop, AliasSetTracker *CurAST, - MemorySSAUpdater *MSSAU, - bool TargetExecutesOncePerLoop, - SinkAndHoistLICMFlags *Flags, - OptimizationRemarkEmitter *ORE) { - // If we don't understand the instruction, bail early. - if (!isHoistableAndSinkableInst(I)) - return false; - - MemorySSA *MSSA = MSSAU ? MSSAU->getMemorySSA() : nullptr; - if (MSSA) - assert(Flags != nullptr && "Flags cannot be null."); - - // Loads have extra constraints we have to verify before we can hoist them. - if (LoadInst *LI = dyn_cast<LoadInst>(&I)) { - if (!LI->isUnordered()) - return false; // Don't sink/hoist volatile or ordered atomic loads! - - // Loads from constant memory are always safe to move, even if they end up - // in the same alias set as something that ends up being modified. - if (AA->pointsToConstantMemory(LI->getOperand(0))) - return true; - if (LI->getMetadata(LLVMContext::MD_invariant_load)) - return true; - - if (LI->isAtomic() && !TargetExecutesOncePerLoop) - return false; // Don't risk duplicating unordered loads - - // This checks for an invariant.start dominating the load. - if (isLoadInvariantInLoop(LI, DT, CurLoop)) - return true; - - bool Invalidated; - if (CurAST) - Invalidated = pointerInvalidatedByLoop(MemoryLocation::get(LI), CurAST, - CurLoop, AA); - else - Invalidated = pointerInvalidatedByLoopWithMSSA( - MSSA, cast<MemoryUse>(MSSA->getMemoryAccess(LI)), CurLoop, *Flags); - // Check loop-invariant address because this may also be a sinkable load - // whose address is not necessarily loop-invariant. - if (ORE && Invalidated && CurLoop->isLoopInvariant(LI->getPointerOperand())) - ORE->emit([&]() { - return OptimizationRemarkMissed( - DEBUG_TYPE, "LoadWithLoopInvariantAddressInvalidated", LI) - << "failed to move load with loop-invariant address " - "because the loop may invalidate its value"; - }); - - return !Invalidated; - } else if (CallInst *CI = dyn_cast<CallInst>(&I)) { - // Don't sink or hoist dbg info; it's legal, but not useful. - if (isa<DbgInfoIntrinsic>(I)) - return false; - - // Don't sink calls which can throw. - if (CI->mayThrow()) - return false; - - using namespace PatternMatch; - if (match(CI, m_Intrinsic<Intrinsic::assume>())) - // Assumes don't actually alias anything or throw - return true; - - // Handle simple cases by querying alias analysis. - FunctionModRefBehavior Behavior = AA->getModRefBehavior(CI); - if (Behavior == FMRB_DoesNotAccessMemory) - return true; - if (AliasAnalysis::onlyReadsMemory(Behavior)) { - // A readonly argmemonly function only reads from memory pointed to by - // it's arguments with arbitrary offsets. If we can prove there are no - // writes to this memory in the loop, we can hoist or sink. - if (AliasAnalysis::onlyAccessesArgPointees(Behavior)) { - // TODO: expand to writeable arguments - for (Value *Op : CI->arg_operands()) - if (Op->getType()->isPointerTy()) { - bool Invalidated; - if (CurAST) - Invalidated = pointerInvalidatedByLoop( - MemoryLocation(Op, LocationSize::unknown(), AAMDNodes()), - CurAST, CurLoop, AA); - else - Invalidated = pointerInvalidatedByLoopWithMSSA( - MSSA, cast<MemoryUse>(MSSA->getMemoryAccess(CI)), CurLoop, - *Flags); - if (Invalidated) - return false; - } - return true; - } - - // If this call only reads from memory and there are no writes to memory - // in the loop, we can hoist or sink the call as appropriate. - if (isReadOnly(CurAST, MSSAU, CurLoop)) - return true; - } - - // FIXME: This should use mod/ref information to see if we can hoist or - // sink the call. - - return false; - } else if (auto *FI = dyn_cast<FenceInst>(&I)) { - // Fences alias (most) everything to provide ordering. For the moment, - // just give up if there are any other memory operations in the loop. - if (CurAST) { - auto Begin = CurAST->begin(); - assert(Begin != CurAST->end() && "must contain FI"); - if (std::next(Begin) != CurAST->end()) - // constant memory for instance, TODO: handle better - return false; - auto *UniqueI = Begin->getUniqueInstruction(); - if (!UniqueI) - // other memory op, give up - return false; - (void)FI; // suppress unused variable warning - assert(UniqueI == FI && "AS must contain FI"); - return true; - } else // MSSAU - return isOnlyMemoryAccess(FI, CurLoop, MSSAU); - } else if (auto *SI = dyn_cast<StoreInst>(&I)) { - if (!SI->isUnordered()) - return false; // Don't sink/hoist volatile or ordered atomic store! - - // We can only hoist a store that we can prove writes a value which is not - // read or overwritten within the loop. For those cases, we fallback to - // load store promotion instead. TODO: We can extend this to cases where - // there is exactly one write to the location and that write dominates an - // arbitrary number of reads in the loop. - if (CurAST) { - auto &AS = CurAST->getAliasSetFor(MemoryLocation::get(SI)); - - if (AS.isRef() || !AS.isMustAlias()) - // Quick exit test, handled by the full path below as well. - return false; - auto *UniqueI = AS.getUniqueInstruction(); - if (!UniqueI) - // other memory op, give up - return false; - assert(UniqueI == SI && "AS must contain SI"); - return true; - } else { // MSSAU - if (isOnlyMemoryAccess(SI, CurLoop, MSSAU)) - return true; - // If there are more accesses than the Promotion cap, give up, we're not - // walking a list that long. - if (Flags->NoOfMemAccTooLarge) - return false; - // Check store only if there's still "quota" to check clobber. - if (Flags->LicmMssaOptCounter >= Flags->LicmMssaOptCap) - return false; - // If there are interfering Uses (i.e. their defining access is in the - // loop), or ordered loads (stored as Defs!), don't move this store. - // Could do better here, but this is conservatively correct. - // TODO: Cache set of Uses on the first walk in runOnLoop, update when - // moving accesses. Can also extend to dominating uses. - auto *SIMD = MSSA->getMemoryAccess(SI); - for (auto *BB : CurLoop->getBlocks()) - if (auto *Accesses = MSSA->getBlockAccesses(BB)) { - for (const auto &MA : *Accesses) - if (const auto *MU = dyn_cast<MemoryUse>(&MA)) { - auto *MD = MU->getDefiningAccess(); - if (!MSSA->isLiveOnEntryDef(MD) && - CurLoop->contains(MD->getBlock())) - return false; - // Disable hoisting past potentially interfering loads. Optimized - // Uses may point to an access outside the loop, as getClobbering - // checks the previous iteration when walking the backedge. - // FIXME: More precise: no Uses that alias SI. - if (!Flags->IsSink && !MSSA->dominates(SIMD, MU)) - return false; - } else if (const auto *MD = dyn_cast<MemoryDef>(&MA)) - if (auto *LI = dyn_cast<LoadInst>(MD->getMemoryInst())) { - (void)LI; // Silence warning. - assert(!LI->isUnordered() && "Expected unordered load"); - return false; - } - } - - auto *Source = MSSA->getSkipSelfWalker()->getClobberingMemoryAccess(SI); - Flags->LicmMssaOptCounter++; - // If there are no clobbering Defs in the loop, store is safe to hoist. - return MSSA->isLiveOnEntryDef(Source) || - !CurLoop->contains(Source->getBlock()); - } - } - - assert(!I.mayReadOrWriteMemory() && "unhandled aliasing"); - - // We've established mechanical ability and aliasing, it's up to the caller - // to check fault safety - return true; -} - -/// Returns true if a PHINode is a trivially replaceable with an -/// Instruction. -/// This is true when all incoming values are that instruction. -/// This pattern occurs most often with LCSSA PHI nodes. -/// -static bool isTriviallyReplaceablePHI(const PHINode &PN, const Instruction &I) { - for (const Value *IncValue : PN.incoming_values()) - if (IncValue != &I) - return false; - - return true; -} - -/// Return true if the instruction is free in the loop. -static bool isFreeInLoop(const Instruction &I, const Loop *CurLoop, - const TargetTransformInfo *TTI) { - - if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&I)) { - if (TTI->getUserCost(GEP) != TargetTransformInfo::TCC_Free) - return false; - // For a GEP, we cannot simply use getUserCost because currently it - // optimistically assume that a GEP will fold into addressing mode - // regardless of its users. - const BasicBlock *BB = GEP->getParent(); - for (const User *U : GEP->users()) { - const Instruction *UI = cast<Instruction>(U); - if (CurLoop->contains(UI) && - (BB != UI->getParent() || - (!isa<StoreInst>(UI) && !isa<LoadInst>(UI)))) - return false; - } - return true; - } else - return TTI->getUserCost(&I) == TargetTransformInfo::TCC_Free; -} - -/// Return true if the only users of this instruction are outside of -/// the loop. If this is true, we can sink the instruction to the exit -/// blocks of the loop. -/// -/// We also return true if the instruction could be folded away in lowering. -/// (e.g., a GEP can be folded into a load as an addressing mode in the loop). -static bool isNotUsedOrFreeInLoop(const Instruction &I, const Loop *CurLoop, - const LoopSafetyInfo *SafetyInfo, - TargetTransformInfo *TTI, bool &FreeInLoop) { - const auto &BlockColors = SafetyInfo->getBlockColors(); - bool IsFree = isFreeInLoop(I, CurLoop, TTI); - for (const User *U : I.users()) { - const Instruction *UI = cast<Instruction>(U); - if (const PHINode *PN = dyn_cast<PHINode>(UI)) { - const BasicBlock *BB = PN->getParent(); - // We cannot sink uses in catchswitches. - if (isa<CatchSwitchInst>(BB->getTerminator())) - return false; - - // We need to sink a callsite to a unique funclet. Avoid sinking if the - // phi use is too muddled. - if (isa<CallInst>(I)) - if (!BlockColors.empty() && - BlockColors.find(const_cast<BasicBlock *>(BB))->second.size() != 1) - return false; - } - - if (CurLoop->contains(UI)) { - if (IsFree) { - FreeInLoop = true; - continue; - } - return false; - } - } - return true; -} - -static Instruction *CloneInstructionInExitBlock( - Instruction &I, BasicBlock &ExitBlock, PHINode &PN, const LoopInfo *LI, - const LoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU) { - Instruction *New; - if (auto *CI = dyn_cast<CallInst>(&I)) { - const auto &BlockColors = SafetyInfo->getBlockColors(); - - // Sinking call-sites need to be handled differently from other - // instructions. The cloned call-site needs a funclet bundle operand - // appropriate for its location in the CFG. - SmallVector<OperandBundleDef, 1> OpBundles; - for (unsigned BundleIdx = 0, BundleEnd = CI->getNumOperandBundles(); - BundleIdx != BundleEnd; ++BundleIdx) { - OperandBundleUse Bundle = CI->getOperandBundleAt(BundleIdx); - if (Bundle.getTagID() == LLVMContext::OB_funclet) - continue; - - OpBundles.emplace_back(Bundle); - } - - if (!BlockColors.empty()) { - const ColorVector &CV = BlockColors.find(&ExitBlock)->second; - assert(CV.size() == 1 && "non-unique color for exit block!"); - BasicBlock *BBColor = CV.front(); - Instruction *EHPad = BBColor->getFirstNonPHI(); - if (EHPad->isEHPad()) - OpBundles.emplace_back("funclet", EHPad); - } - - New = CallInst::Create(CI, OpBundles); - } else { - New = I.clone(); - } - - ExitBlock.getInstList().insert(ExitBlock.getFirstInsertionPt(), New); - if (!I.getName().empty()) - New->setName(I.getName() + ".le"); - - MemoryAccess *OldMemAcc; - if (MSSAU && (OldMemAcc = MSSAU->getMemorySSA()->getMemoryAccess(&I))) { - // Create a new MemoryAccess and let MemorySSA set its defining access. - MemoryAccess *NewMemAcc = MSSAU->createMemoryAccessInBB( - New, nullptr, New->getParent(), MemorySSA::Beginning); - if (NewMemAcc) { - if (auto *MemDef = dyn_cast<MemoryDef>(NewMemAcc)) - MSSAU->insertDef(MemDef, /*RenameUses=*/true); - else { - auto *MemUse = cast<MemoryUse>(NewMemAcc); - MSSAU->insertUse(MemUse); - } - } - } - - // Build LCSSA PHI nodes for any in-loop operands. Note that this is - // particularly cheap because we can rip off the PHI node that we're - // replacing for the number and blocks of the predecessors. - // OPT: If this shows up in a profile, we can instead finish sinking all - // invariant instructions, and then walk their operands to re-establish - // LCSSA. That will eliminate creating PHI nodes just to nuke them when - // sinking bottom-up. - for (User::op_iterator OI = New->op_begin(), OE = New->op_end(); OI != OE; - ++OI) - if (Instruction *OInst = dyn_cast<Instruction>(*OI)) - if (Loop *OLoop = LI->getLoopFor(OInst->getParent())) - if (!OLoop->contains(&PN)) { - PHINode *OpPN = - PHINode::Create(OInst->getType(), PN.getNumIncomingValues(), - OInst->getName() + ".lcssa", &ExitBlock.front()); - for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) - OpPN->addIncoming(OInst, PN.getIncomingBlock(i)); - *OI = OpPN; - } - return New; -} - -static void eraseInstruction(Instruction &I, ICFLoopSafetyInfo &SafetyInfo, - AliasSetTracker *AST, MemorySSAUpdater *MSSAU) { - if (AST) - AST->deleteValue(&I); - if (MSSAU) - MSSAU->removeMemoryAccess(&I); - SafetyInfo.removeInstruction(&I); - I.eraseFromParent(); -} - -static void moveInstructionBefore(Instruction &I, Instruction &Dest, - ICFLoopSafetyInfo &SafetyInfo, - MemorySSAUpdater *MSSAU) { - SafetyInfo.removeInstruction(&I); - SafetyInfo.insertInstructionTo(&I, Dest.getParent()); - I.moveBefore(&Dest); - if (MSSAU) - if (MemoryUseOrDef *OldMemAcc = cast_or_null<MemoryUseOrDef>( - MSSAU->getMemorySSA()->getMemoryAccess(&I))) - MSSAU->moveToPlace(OldMemAcc, Dest.getParent(), MemorySSA::End); -} - -static Instruction *sinkThroughTriviallyReplaceablePHI( - PHINode *TPN, Instruction *I, LoopInfo *LI, - SmallDenseMap<BasicBlock *, Instruction *, 32> &SunkCopies, - const LoopSafetyInfo *SafetyInfo, const Loop *CurLoop, - MemorySSAUpdater *MSSAU) { - assert(isTriviallyReplaceablePHI(*TPN, *I) && - "Expect only trivially replaceable PHI"); - BasicBlock *ExitBlock = TPN->getParent(); - Instruction *New; - auto It = SunkCopies.find(ExitBlock); - if (It != SunkCopies.end()) - New = It->second; - else - New = SunkCopies[ExitBlock] = CloneInstructionInExitBlock( - *I, *ExitBlock, *TPN, LI, SafetyInfo, MSSAU); - return New; -} - -static bool canSplitPredecessors(PHINode *PN, LoopSafetyInfo *SafetyInfo) { - BasicBlock *BB = PN->getParent(); - if (!BB->canSplitPredecessors()) - return false; - // It's not impossible to split EHPad blocks, but if BlockColors already exist - // it require updating BlockColors for all offspring blocks accordingly. By - // skipping such corner case, we can make updating BlockColors after splitting - // predecessor fairly simple. - if (!SafetyInfo->getBlockColors().empty() && BB->getFirstNonPHI()->isEHPad()) - return false; - for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { - BasicBlock *BBPred = *PI; - if (isa<IndirectBrInst>(BBPred->getTerminator())) - return false; - } - return true; -} - -static void splitPredecessorsOfLoopExit(PHINode *PN, DominatorTree *DT, - LoopInfo *LI, const Loop *CurLoop, - LoopSafetyInfo *SafetyInfo, - MemorySSAUpdater *MSSAU) { -#ifndef NDEBUG - SmallVector<BasicBlock *, 32> ExitBlocks; - CurLoop->getUniqueExitBlocks(ExitBlocks); - SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(), - ExitBlocks.end()); -#endif - BasicBlock *ExitBB = PN->getParent(); - assert(ExitBlockSet.count(ExitBB) && "Expect the PHI is in an exit block."); - - // Split predecessors of the loop exit to make instructions in the loop are - // exposed to exit blocks through trivially replaceable PHIs while keeping the - // loop in the canonical form where each predecessor of each exit block should - // be contained within the loop. For example, this will convert the loop below - // from - // - // LB1: - // %v1 = - // br %LE, %LB2 - // LB2: - // %v2 = - // br %LE, %LB1 - // LE: - // %p = phi [%v1, %LB1], [%v2, %LB2] <-- non-trivially replaceable - // - // to - // - // LB1: - // %v1 = - // br %LE.split, %LB2 - // LB2: - // %v2 = - // br %LE.split2, %LB1 - // LE.split: - // %p1 = phi [%v1, %LB1] <-- trivially replaceable - // br %LE - // LE.split2: - // %p2 = phi [%v2, %LB2] <-- trivially replaceable - // br %LE - // LE: - // %p = phi [%p1, %LE.split], [%p2, %LE.split2] - // - const auto &BlockColors = SafetyInfo->getBlockColors(); - SmallSetVector<BasicBlock *, 8> PredBBs(pred_begin(ExitBB), pred_end(ExitBB)); - while (!PredBBs.empty()) { - BasicBlock *PredBB = *PredBBs.begin(); - assert(CurLoop->contains(PredBB) && - "Expect all predecessors are in the loop"); - if (PN->getBasicBlockIndex(PredBB) >= 0) { - BasicBlock *NewPred = SplitBlockPredecessors( - ExitBB, PredBB, ".split.loop.exit", DT, LI, MSSAU, true); - // Since we do not allow splitting EH-block with BlockColors in - // canSplitPredecessors(), we can simply assign predecessor's color to - // the new block. - if (!BlockColors.empty()) - // Grab a reference to the ColorVector to be inserted before getting the - // reference to the vector we are copying because inserting the new - // element in BlockColors might cause the map to be reallocated. - SafetyInfo->copyColors(NewPred, PredBB); - } - PredBBs.remove(PredBB); - } -} - -/// When an instruction is found to only be used outside of the loop, this -/// function moves it to the exit blocks and patches up SSA form as needed. -/// This method is guaranteed to remove the original instruction from its -/// position, and may either delete it or move it to outside of the loop. -/// -static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT, - const Loop *CurLoop, ICFLoopSafetyInfo *SafetyInfo, - MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE) { - LLVM_DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n"); - ORE->emit([&]() { - return OptimizationRemark(DEBUG_TYPE, "InstSunk", &I) - << "sinking " << ore::NV("Inst", &I); - }); - bool Changed = false; - if (isa<LoadInst>(I)) - ++NumMovedLoads; - else if (isa<CallInst>(I)) - ++NumMovedCalls; - ++NumSunk; - - // Iterate over users to be ready for actual sinking. Replace users via - // unreachable blocks with undef and make all user PHIs trivially replaceable. - SmallPtrSet<Instruction *, 8> VisitedUsers; - for (Value::user_iterator UI = I.user_begin(), UE = I.user_end(); UI != UE;) { - auto *User = cast<Instruction>(*UI); - Use &U = UI.getUse(); - ++UI; - - if (VisitedUsers.count(User) || CurLoop->contains(User)) - continue; - - if (!DT->isReachableFromEntry(User->getParent())) { - U = UndefValue::get(I.getType()); - Changed = true; - continue; - } - - // The user must be a PHI node. - PHINode *PN = cast<PHINode>(User); - - // Surprisingly, instructions can be used outside of loops without any - // exits. This can only happen in PHI nodes if the incoming block is - // unreachable. - BasicBlock *BB = PN->getIncomingBlock(U); - if (!DT->isReachableFromEntry(BB)) { - U = UndefValue::get(I.getType()); - Changed = true; - continue; - } - - VisitedUsers.insert(PN); - if (isTriviallyReplaceablePHI(*PN, I)) - continue; - - if (!canSplitPredecessors(PN, SafetyInfo)) - return Changed; - - // Split predecessors of the PHI so that we can make users trivially - // replaceable. - splitPredecessorsOfLoopExit(PN, DT, LI, CurLoop, SafetyInfo, MSSAU); - - // Should rebuild the iterators, as they may be invalidated by - // splitPredecessorsOfLoopExit(). - UI = I.user_begin(); - UE = I.user_end(); - } - - if (VisitedUsers.empty()) - return Changed; - -#ifndef NDEBUG - SmallVector<BasicBlock *, 32> ExitBlocks; - CurLoop->getUniqueExitBlocks(ExitBlocks); - SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(), - ExitBlocks.end()); -#endif - - // Clones of this instruction. Don't create more than one per exit block! - SmallDenseMap<BasicBlock *, Instruction *, 32> SunkCopies; - - // If this instruction is only used outside of the loop, then all users are - // PHI nodes in exit blocks due to LCSSA form. Just RAUW them with clones of - // the instruction. - SmallSetVector<User*, 8> Users(I.user_begin(), I.user_end()); - for (auto *UI : Users) { - auto *User = cast<Instruction>(UI); - - if (CurLoop->contains(User)) - continue; - - PHINode *PN = cast<PHINode>(User); - assert(ExitBlockSet.count(PN->getParent()) && - "The LCSSA PHI is not in an exit block!"); - // The PHI must be trivially replaceable. - Instruction *New = sinkThroughTriviallyReplaceablePHI( - PN, &I, LI, SunkCopies, SafetyInfo, CurLoop, MSSAU); - PN->replaceAllUsesWith(New); - eraseInstruction(*PN, *SafetyInfo, nullptr, nullptr); - Changed = true; - } - return Changed; -} - -/// When an instruction is found to only use loop invariant operands that -/// is safe to hoist, this instruction is called to do the dirty work. -/// -static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop, - BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo, - MemorySSAUpdater *MSSAU, OptimizationRemarkEmitter *ORE) { - LLVM_DEBUG(dbgs() << "LICM hoisting to " << Dest->getName() << ": " << I - << "\n"); - ORE->emit([&]() { - return OptimizationRemark(DEBUG_TYPE, "Hoisted", &I) << "hoisting " - << ore::NV("Inst", &I); - }); - - // Metadata can be dependent on conditions we are hoisting above. - // Conservatively strip all metadata on the instruction unless we were - // guaranteed to execute I if we entered the loop, in which case the metadata - // is valid in the loop preheader. - if (I.hasMetadataOtherThanDebugLoc() && - // The check on hasMetadataOtherThanDebugLoc is to prevent us from burning - // time in isGuaranteedToExecute if we don't actually have anything to - // drop. It is a compile time optimization, not required for correctness. - !SafetyInfo->isGuaranteedToExecute(I, DT, CurLoop)) - I.dropUnknownNonDebugMetadata(); - - if (isa<PHINode>(I)) - // Move the new node to the end of the phi list in the destination block. - moveInstructionBefore(I, *Dest->getFirstNonPHI(), *SafetyInfo, MSSAU); - else - // Move the new node to the destination block, before its terminator. - moveInstructionBefore(I, *Dest->getTerminator(), *SafetyInfo, MSSAU); - - // Apply line 0 debug locations when we are moving instructions to different - // basic blocks because we want to avoid jumpy line tables. - if (const DebugLoc &DL = I.getDebugLoc()) - I.setDebugLoc(DebugLoc::get(0, 0, DL.getScope(), DL.getInlinedAt())); - - if (isa<LoadInst>(I)) - ++NumMovedLoads; - else if (isa<CallInst>(I)) - ++NumMovedCalls; - ++NumHoisted; -} - -/// Only sink or hoist an instruction if it is not a trapping instruction, -/// or if the instruction is known not to trap when moved to the preheader. -/// or if it is a trapping instruction and is guaranteed to execute. -static bool isSafeToExecuteUnconditionally(Instruction &Inst, - const DominatorTree *DT, - const Loop *CurLoop, - const LoopSafetyInfo *SafetyInfo, - OptimizationRemarkEmitter *ORE, - const Instruction *CtxI) { - if (isSafeToSpeculativelyExecute(&Inst, CtxI, DT)) - return true; - - bool GuaranteedToExecute = - SafetyInfo->isGuaranteedToExecute(Inst, DT, CurLoop); - - if (!GuaranteedToExecute) { - auto *LI = dyn_cast<LoadInst>(&Inst); - if (LI && CurLoop->isLoopInvariant(LI->getPointerOperand())) - ORE->emit([&]() { - return OptimizationRemarkMissed( - DEBUG_TYPE, "LoadWithLoopInvariantAddressCondExecuted", LI) - << "failed to hoist load with loop-invariant address " - "because load is conditionally executed"; - }); - } - - return GuaranteedToExecute; -} - -namespace { -class LoopPromoter : public LoadAndStorePromoter { - Value *SomePtr; // Designated pointer to store to. - const SmallSetVector<Value *, 8> &PointerMustAliases; - SmallVectorImpl<BasicBlock *> &LoopExitBlocks; - SmallVectorImpl<Instruction *> &LoopInsertPts; - SmallVectorImpl<MemoryAccess *> &MSSAInsertPts; - PredIteratorCache &PredCache; - AliasSetTracker &AST; - MemorySSAUpdater *MSSAU; - LoopInfo &LI; - DebugLoc DL; - int Alignment; - bool UnorderedAtomic; - AAMDNodes AATags; - ICFLoopSafetyInfo &SafetyInfo; - - Value *maybeInsertLCSSAPHI(Value *V, BasicBlock *BB) const { - if (Instruction *I = dyn_cast<Instruction>(V)) - if (Loop *L = LI.getLoopFor(I->getParent())) - if (!L->contains(BB)) { - // We need to create an LCSSA PHI node for the incoming value and - // store that. - PHINode *PN = PHINode::Create(I->getType(), PredCache.size(BB), - I->getName() + ".lcssa", &BB->front()); - for (BasicBlock *Pred : PredCache.get(BB)) - PN->addIncoming(I, Pred); - return PN; - } - return V; - } - -public: - LoopPromoter(Value *SP, ArrayRef<const Instruction *> Insts, SSAUpdater &S, - const SmallSetVector<Value *, 8> &PMA, - SmallVectorImpl<BasicBlock *> &LEB, - SmallVectorImpl<Instruction *> &LIP, - SmallVectorImpl<MemoryAccess *> &MSSAIP, PredIteratorCache &PIC, - AliasSetTracker &ast, MemorySSAUpdater *MSSAU, LoopInfo &li, - DebugLoc dl, int alignment, bool UnorderedAtomic, - const AAMDNodes &AATags, ICFLoopSafetyInfo &SafetyInfo) - : LoadAndStorePromoter(Insts, S), SomePtr(SP), PointerMustAliases(PMA), - LoopExitBlocks(LEB), LoopInsertPts(LIP), MSSAInsertPts(MSSAIP), - PredCache(PIC), AST(ast), MSSAU(MSSAU), LI(li), DL(std::move(dl)), - Alignment(alignment), UnorderedAtomic(UnorderedAtomic), AATags(AATags), - SafetyInfo(SafetyInfo) {} - - bool isInstInList(Instruction *I, - const SmallVectorImpl<Instruction *> &) const override { - Value *Ptr; - if (LoadInst *LI = dyn_cast<LoadInst>(I)) - Ptr = LI->getOperand(0); - else - Ptr = cast<StoreInst>(I)->getPointerOperand(); - return PointerMustAliases.count(Ptr); - } - - void doExtraRewritesBeforeFinalDeletion() override { - // Insert stores after in the loop exit blocks. Each exit block gets a - // store of the live-out values that feed them. Since we've already told - // the SSA updater about the defs in the loop and the preheader - // definition, it is all set and we can start using it. - for (unsigned i = 0, e = LoopExitBlocks.size(); i != e; ++i) { - BasicBlock *ExitBlock = LoopExitBlocks[i]; - Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock); - LiveInValue = maybeInsertLCSSAPHI(LiveInValue, ExitBlock); - Value *Ptr = maybeInsertLCSSAPHI(SomePtr, ExitBlock); - Instruction *InsertPos = LoopInsertPts[i]; - StoreInst *NewSI = new StoreInst(LiveInValue, Ptr, InsertPos); - if (UnorderedAtomic) - NewSI->setOrdering(AtomicOrdering::Unordered); - NewSI->setAlignment(Alignment); - NewSI->setDebugLoc(DL); - if (AATags) - NewSI->setAAMetadata(AATags); - - if (MSSAU) { - MemoryAccess *MSSAInsertPoint = MSSAInsertPts[i]; - MemoryAccess *NewMemAcc; - if (!MSSAInsertPoint) { - NewMemAcc = MSSAU->createMemoryAccessInBB( - NewSI, nullptr, NewSI->getParent(), MemorySSA::Beginning); - } else { - NewMemAcc = - MSSAU->createMemoryAccessAfter(NewSI, nullptr, MSSAInsertPoint); - } - MSSAInsertPts[i] = NewMemAcc; - MSSAU->insertDef(cast<MemoryDef>(NewMemAcc), true); - // FIXME: true for safety, false may still be correct. - } - } - } - - void replaceLoadWithValue(LoadInst *LI, Value *V) const override { - // Update alias analysis. - AST.copyValue(LI, V); - } - void instructionDeleted(Instruction *I) const override { - SafetyInfo.removeInstruction(I); - AST.deleteValue(I); - if (MSSAU) - MSSAU->removeMemoryAccess(I); - } -}; - - -/// Return true iff we can prove that a caller of this function can not inspect -/// the contents of the provided object in a well defined program. -bool isKnownNonEscaping(Value *Object, const TargetLibraryInfo *TLI) { - if (isa<AllocaInst>(Object)) - // Since the alloca goes out of scope, we know the caller can't retain a - // reference to it and be well defined. Thus, we don't need to check for - // capture. - return true; - - // For all other objects we need to know that the caller can't possibly - // have gotten a reference to the object. There are two components of - // that: - // 1) Object can't be escaped by this function. This is what - // PointerMayBeCaptured checks. - // 2) Object can't have been captured at definition site. For this, we - // need to know the return value is noalias. At the moment, we use a - // weaker condition and handle only AllocLikeFunctions (which are - // known to be noalias). TODO - return isAllocLikeFn(Object, TLI) && - !PointerMayBeCaptured(Object, true, true); -} - -} // namespace - -/// Try to promote memory values to scalars by sinking stores out of the -/// loop and moving loads to before the loop. We do this by looping over -/// the stores in the loop, looking for stores to Must pointers which are -/// loop invariant. -/// -bool llvm::promoteLoopAccessesToScalars( - const SmallSetVector<Value *, 8> &PointerMustAliases, - SmallVectorImpl<BasicBlock *> &ExitBlocks, - SmallVectorImpl<Instruction *> &InsertPts, - SmallVectorImpl<MemoryAccess *> &MSSAInsertPts, PredIteratorCache &PIC, - LoopInfo *LI, DominatorTree *DT, const TargetLibraryInfo *TLI, - Loop *CurLoop, AliasSetTracker *CurAST, MemorySSAUpdater *MSSAU, - ICFLoopSafetyInfo *SafetyInfo, OptimizationRemarkEmitter *ORE) { - // Verify inputs. - assert(LI != nullptr && DT != nullptr && CurLoop != nullptr && - CurAST != nullptr && SafetyInfo != nullptr && - "Unexpected Input to promoteLoopAccessesToScalars"); - - Value *SomePtr = *PointerMustAliases.begin(); - BasicBlock *Preheader = CurLoop->getLoopPreheader(); - - // It is not safe to promote a load/store from the loop if the load/store is - // conditional. For example, turning: - // - // for () { if (c) *P += 1; } - // - // into: - // - // tmp = *P; for () { if (c) tmp +=1; } *P = tmp; - // - // is not safe, because *P may only be valid to access if 'c' is true. - // - // The safety property divides into two parts: - // p1) The memory may not be dereferenceable on entry to the loop. In this - // case, we can't insert the required load in the preheader. - // p2) The memory model does not allow us to insert a store along any dynamic - // path which did not originally have one. - // - // If at least one store is guaranteed to execute, both properties are - // satisfied, and promotion is legal. - // - // This, however, is not a necessary condition. Even if no store/load is - // guaranteed to execute, we can still establish these properties. - // We can establish (p1) by proving that hoisting the load into the preheader - // is safe (i.e. proving dereferenceability on all paths through the loop). We - // can use any access within the alias set to prove dereferenceability, - // since they're all must alias. - // - // There are two ways establish (p2): - // a) Prove the location is thread-local. In this case the memory model - // requirement does not apply, and stores are safe to insert. - // b) Prove a store dominates every exit block. In this case, if an exit - // blocks is reached, the original dynamic path would have taken us through - // the store, so inserting a store into the exit block is safe. Note that this - // is different from the store being guaranteed to execute. For instance, - // if an exception is thrown on the first iteration of the loop, the original - // store is never executed, but the exit blocks are not executed either. - - bool DereferenceableInPH = false; - bool SafeToInsertStore = false; - - SmallVector<Instruction *, 64> LoopUses; - - // We start with an alignment of one and try to find instructions that allow - // us to prove better alignment. - unsigned Alignment = 1; - // Keep track of which types of access we see - bool SawUnorderedAtomic = false; - bool SawNotAtomic = false; - AAMDNodes AATags; - - const DataLayout &MDL = Preheader->getModule()->getDataLayout(); - - bool IsKnownThreadLocalObject = false; - if (SafetyInfo->anyBlockMayThrow()) { - // If a loop can throw, we have to insert a store along each unwind edge. - // That said, we can't actually make the unwind edge explicit. Therefore, - // we have to prove that the store is dead along the unwind edge. We do - // this by proving that the caller can't have a reference to the object - // after return and thus can't possibly load from the object. - Value *Object = GetUnderlyingObject(SomePtr, MDL); - if (!isKnownNonEscaping(Object, TLI)) - return false; - // Subtlety: Alloca's aren't visible to callers, but *are* potentially - // visible to other threads if captured and used during their lifetimes. - IsKnownThreadLocalObject = !isa<AllocaInst>(Object); - } - - // Check that all of the pointers in the alias set have the same type. We - // cannot (yet) promote a memory location that is loaded and stored in - // different sizes. While we are at it, collect alignment and AA info. - for (Value *ASIV : PointerMustAliases) { - // Check that all of the pointers in the alias set have the same type. We - // cannot (yet) promote a memory location that is loaded and stored in - // different sizes. - if (SomePtr->getType() != ASIV->getType()) - return false; - - for (User *U : ASIV->users()) { - // Ignore instructions that are outside the loop. - Instruction *UI = dyn_cast<Instruction>(U); - if (!UI || !CurLoop->contains(UI)) - continue; - - // If there is an non-load/store instruction in the loop, we can't promote - // it. - if (LoadInst *Load = dyn_cast<LoadInst>(UI)) { - if (!Load->isUnordered()) - return false; - - SawUnorderedAtomic |= Load->isAtomic(); - SawNotAtomic |= !Load->isAtomic(); - - unsigned InstAlignment = Load->getAlignment(); - if (!InstAlignment) - InstAlignment = - MDL.getABITypeAlignment(Load->getType()); - - // Note that proving a load safe to speculate requires proving - // sufficient alignment at the target location. Proving it guaranteed - // to execute does as well. Thus we can increase our guaranteed - // alignment as well. - if (!DereferenceableInPH || (InstAlignment > Alignment)) - if (isSafeToExecuteUnconditionally(*Load, DT, CurLoop, SafetyInfo, - ORE, Preheader->getTerminator())) { - DereferenceableInPH = true; - Alignment = std::max(Alignment, InstAlignment); - } - } else if (const StoreInst *Store = dyn_cast<StoreInst>(UI)) { - // Stores *of* the pointer are not interesting, only stores *to* the - // pointer. - if (UI->getOperand(1) != ASIV) - continue; - if (!Store->isUnordered()) - return false; - - SawUnorderedAtomic |= Store->isAtomic(); - SawNotAtomic |= !Store->isAtomic(); - - // If the store is guaranteed to execute, both properties are satisfied. - // We may want to check if a store is guaranteed to execute even if we - // already know that promotion is safe, since it may have higher - // alignment than any other guaranteed stores, in which case we can - // raise the alignment on the promoted store. - unsigned InstAlignment = Store->getAlignment(); - if (!InstAlignment) - InstAlignment = - MDL.getABITypeAlignment(Store->getValueOperand()->getType()); - - if (!DereferenceableInPH || !SafeToInsertStore || - (InstAlignment > Alignment)) { - if (SafetyInfo->isGuaranteedToExecute(*UI, DT, CurLoop)) { - DereferenceableInPH = true; - SafeToInsertStore = true; - Alignment = std::max(Alignment, InstAlignment); - } - } - - // If a store dominates all exit blocks, it is safe to sink. - // As explained above, if an exit block was executed, a dominating - // store must have been executed at least once, so we are not - // introducing stores on paths that did not have them. - // Note that this only looks at explicit exit blocks. If we ever - // start sinking stores into unwind edges (see above), this will break. - if (!SafeToInsertStore) - SafeToInsertStore = llvm::all_of(ExitBlocks, [&](BasicBlock *Exit) { - return DT->dominates(Store->getParent(), Exit); - }); - - // If the store is not guaranteed to execute, we may still get - // deref info through it. - if (!DereferenceableInPH) { - DereferenceableInPH = isDereferenceableAndAlignedPointer( - Store->getPointerOperand(), Store->getValueOperand()->getType(), - Store->getAlignment(), MDL, Preheader->getTerminator(), DT); - } - } else - return false; // Not a load or store. - - // Merge the AA tags. - if (LoopUses.empty()) { - // On the first load/store, just take its AA tags. - UI->getAAMetadata(AATags); - } else if (AATags) { - UI->getAAMetadata(AATags, /* Merge = */ true); - } - - LoopUses.push_back(UI); - } - } - - // If we found both an unordered atomic instruction and a non-atomic memory - // access, bail. We can't blindly promote non-atomic to atomic since we - // might not be able to lower the result. We can't downgrade since that - // would violate memory model. Also, align 0 is an error for atomics. - if (SawUnorderedAtomic && SawNotAtomic) - return false; - - // If we're inserting an atomic load in the preheader, we must be able to - // lower it. We're only guaranteed to be able to lower naturally aligned - // atomics. - auto *SomePtrElemType = SomePtr->getType()->getPointerElementType(); - if (SawUnorderedAtomic && - Alignment < MDL.getTypeStoreSize(SomePtrElemType)) - return false; - - // If we couldn't prove we can hoist the load, bail. - if (!DereferenceableInPH) - return false; - - // We know we can hoist the load, but don't have a guaranteed store. - // Check whether the location is thread-local. If it is, then we can insert - // stores along paths which originally didn't have them without violating the - // memory model. - if (!SafeToInsertStore) { - if (IsKnownThreadLocalObject) - SafeToInsertStore = true; - else { - Value *Object = GetUnderlyingObject(SomePtr, MDL); - SafeToInsertStore = - (isAllocLikeFn(Object, TLI) || isa<AllocaInst>(Object)) && - !PointerMayBeCaptured(Object, true, true); - } - } - - // If we've still failed to prove we can sink the store, give up. - if (!SafeToInsertStore) - return false; - - // Otherwise, this is safe to promote, lets do it! - LLVM_DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " << *SomePtr - << '\n'); - ORE->emit([&]() { - return OptimizationRemark(DEBUG_TYPE, "PromoteLoopAccessesToScalar", - LoopUses[0]) - << "Moving accesses to memory location out of the loop"; - }); - ++NumPromoted; - - // Grab a debug location for the inserted loads/stores; given that the - // inserted loads/stores have little relation to the original loads/stores, - // this code just arbitrarily picks a location from one, since any debug - // location is better than none. - DebugLoc DL = LoopUses[0]->getDebugLoc(); - - // We use the SSAUpdater interface to insert phi nodes as required. - SmallVector<PHINode *, 16> NewPHIs; - SSAUpdater SSA(&NewPHIs); - LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks, - InsertPts, MSSAInsertPts, PIC, *CurAST, MSSAU, *LI, DL, - Alignment, SawUnorderedAtomic, AATags, *SafetyInfo); - - // Set up the preheader to have a definition of the value. It is the live-out - // value from the preheader that uses in the loop will use. - LoadInst *PreheaderLoad = new LoadInst( - SomePtr->getType()->getPointerElementType(), SomePtr, - SomePtr->getName() + ".promoted", Preheader->getTerminator()); - if (SawUnorderedAtomic) - PreheaderLoad->setOrdering(AtomicOrdering::Unordered); - PreheaderLoad->setAlignment(Alignment); - PreheaderLoad->setDebugLoc(DL); - if (AATags) - PreheaderLoad->setAAMetadata(AATags); - SSA.AddAvailableValue(Preheader, PreheaderLoad); - - MemoryAccess *PreheaderLoadMemoryAccess; - if (MSSAU) { - PreheaderLoadMemoryAccess = MSSAU->createMemoryAccessInBB( - PreheaderLoad, nullptr, PreheaderLoad->getParent(), MemorySSA::End); - MemoryUse *NewMemUse = cast<MemoryUse>(PreheaderLoadMemoryAccess); - MSSAU->insertUse(NewMemUse); - } - - // Rewrite all the loads in the loop and remember all the definitions from - // stores in the loop. - Promoter.run(LoopUses); - - if (MSSAU && VerifyMemorySSA) - MSSAU->getMemorySSA()->verifyMemorySSA(); - // If the SSAUpdater didn't use the load in the preheader, just zap it now. - if (PreheaderLoad->use_empty()) - eraseInstruction(*PreheaderLoad, *SafetyInfo, CurAST, MSSAU); - - return true; -} - -/// Returns an owning pointer to an alias set which incorporates aliasing info -/// from L and all subloops of L. -/// FIXME: In new pass manager, there is no helper function to handle loop -/// analysis such as cloneBasicBlockAnalysis, so the AST needs to be recomputed -/// from scratch for every loop. Hook up with the helper functions when -/// available in the new pass manager to avoid redundant computation. -std::unique_ptr<AliasSetTracker> -LoopInvariantCodeMotion::collectAliasInfoForLoop(Loop *L, LoopInfo *LI, - AliasAnalysis *AA) { - std::unique_ptr<AliasSetTracker> CurAST; - SmallVector<Loop *, 4> RecomputeLoops; - for (Loop *InnerL : L->getSubLoops()) { - auto MapI = LoopToAliasSetMap.find(InnerL); - // If the AST for this inner loop is missing it may have been merged into - // some other loop's AST and then that loop unrolled, and so we need to - // recompute it. - if (MapI == LoopToAliasSetMap.end()) { - RecomputeLoops.push_back(InnerL); - continue; - } - std::unique_ptr<AliasSetTracker> InnerAST = std::move(MapI->second); - - if (CurAST) { - // What if InnerLoop was modified by other passes ? - // Once we've incorporated the inner loop's AST into ours, we don't need - // the subloop's anymore. - CurAST->add(*InnerAST); - } else { - CurAST = std::move(InnerAST); - } - LoopToAliasSetMap.erase(MapI); - } - if (!CurAST) - CurAST = make_unique<AliasSetTracker>(*AA); - - // Add everything from the sub loops that are no longer directly available. - for (Loop *InnerL : RecomputeLoops) - for (BasicBlock *BB : InnerL->blocks()) - CurAST->add(*BB); - - // And merge in this loop (without anything from inner loops). - for (BasicBlock *BB : L->blocks()) - if (LI->getLoopFor(BB) == L) - CurAST->add(*BB); - - return CurAST; -} - -std::unique_ptr<AliasSetTracker> -LoopInvariantCodeMotion::collectAliasInfoForLoopWithMSSA( - Loop *L, AliasAnalysis *AA, MemorySSAUpdater *MSSAU) { - auto *MSSA = MSSAU->getMemorySSA(); - auto CurAST = make_unique<AliasSetTracker>(*AA, MSSA, L); - CurAST->addAllInstructionsInLoopUsingMSSA(); - return CurAST; -} - -/// Simple analysis hook. Clone alias set info. -/// -void LegacyLICMPass::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, - Loop *L) { - auto ASTIt = LICM.getLoopToAliasSetMap().find(L); - if (ASTIt == LICM.getLoopToAliasSetMap().end()) - return; - - ASTIt->second->copyValue(From, To); -} - -/// Simple Analysis hook. Delete value V from alias set -/// -void LegacyLICMPass::deleteAnalysisValue(Value *V, Loop *L) { - auto ASTIt = LICM.getLoopToAliasSetMap().find(L); - if (ASTIt == LICM.getLoopToAliasSetMap().end()) - return; - - ASTIt->second->deleteValue(V); -} - -/// Simple Analysis hook. Delete value L from alias set map. -/// -void LegacyLICMPass::deleteAnalysisLoop(Loop *L) { - if (!LICM.getLoopToAliasSetMap().count(L)) - return; - - LICM.getLoopToAliasSetMap().erase(L); -} - -static bool pointerInvalidatedByLoop(MemoryLocation MemLoc, - AliasSetTracker *CurAST, Loop *CurLoop, - AliasAnalysis *AA) { - // First check to see if any of the basic blocks in CurLoop invalidate *V. - bool isInvalidatedAccordingToAST = CurAST->getAliasSetFor(MemLoc).isMod(); - - if (!isInvalidatedAccordingToAST || !LICMN2Theshold) - return isInvalidatedAccordingToAST; - - // Check with a diagnostic analysis if we can refine the information above. - // This is to identify the limitations of using the AST. - // The alias set mechanism used by LICM has a major weakness in that it - // combines all things which may alias into a single set *before* asking - // modref questions. As a result, a single readonly call within a loop will - // collapse all loads and stores into a single alias set and report - // invalidation if the loop contains any store. For example, readonly calls - // with deopt states have this form and create a general alias set with all - // loads and stores. In order to get any LICM in loops containing possible - // deopt states we need a more precise invalidation of checking the mod ref - // info of each instruction within the loop and LI. This has a complexity of - // O(N^2), so currently, it is used only as a diagnostic tool since the - // default value of LICMN2Threshold is zero. - - // Don't look at nested loops. - if (CurLoop->begin() != CurLoop->end()) - return true; - - int N = 0; - for (BasicBlock *BB : CurLoop->getBlocks()) - for (Instruction &I : *BB) { - if (N >= LICMN2Theshold) { - LLVM_DEBUG(dbgs() << "Alasing N2 threshold exhausted for " - << *(MemLoc.Ptr) << "\n"); - return true; - } - N++; - auto Res = AA->getModRefInfo(&I, MemLoc); - if (isModSet(Res)) { - LLVM_DEBUG(dbgs() << "Aliasing failed on " << I << " for " - << *(MemLoc.Ptr) << "\n"); - return true; - } - } - LLVM_DEBUG(dbgs() << "Aliasing okay for " << *(MemLoc.Ptr) << "\n"); - return false; -} - -static bool pointerInvalidatedByLoopWithMSSA(MemorySSA *MSSA, MemoryUse *MU, - Loop *CurLoop, - SinkAndHoistLICMFlags &Flags) { - // For hoisting, use the walker to determine safety - if (!Flags.IsSink) { - MemoryAccess *Source; - // See declaration of SetLicmMssaOptCap for usage details. - if (Flags.LicmMssaOptCounter >= Flags.LicmMssaOptCap) - Source = MU->getDefiningAccess(); - else { - Source = MSSA->getSkipSelfWalker()->getClobberingMemoryAccess(MU); - Flags.LicmMssaOptCounter++; - } - return !MSSA->isLiveOnEntryDef(Source) && - CurLoop->contains(Source->getBlock()); - } - - // For sinking, we'd need to check all Defs below this use. The getClobbering - // call will look on the backedge of the loop, but will check aliasing with - // the instructions on the previous iteration. - // For example: - // for (i ... ) - // load a[i] ( Use (LoE) - // store a[i] ( 1 = Def (2), with 2 = Phi for the loop. - // i++; - // The load sees no clobbering inside the loop, as the backedge alias check - // does phi translation, and will check aliasing against store a[i-1]. - // However sinking the load outside the loop, below the store is incorrect. - - // For now, only sink if there are no Defs in the loop, and the existing ones - // precede the use and are in the same block. - // FIXME: Increase precision: Safe to sink if Use post dominates the Def; - // needs PostDominatorTreeAnalysis. - // FIXME: More precise: no Defs that alias this Use. - if (Flags.NoOfMemAccTooLarge) - return true; - for (auto *BB : CurLoop->getBlocks()) - if (auto *Accesses = MSSA->getBlockDefs(BB)) - for (const auto &MA : *Accesses) - if (const auto *MD = dyn_cast<MemoryDef>(&MA)) - if (MU->getBlock() != MD->getBlock() || - !MSSA->locallyDominates(MD, MU)) - return true; - return false; -} - -/// Little predicate that returns true if the specified basic block is in -/// a subloop of the current one, not the current one itself. -/// -static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI) { - assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop"); - return LI->getLoopFor(BB) != CurLoop; -} |